This is an application for the Michigan State University (MSU) Department of Neurology to become a clinical center in the Parkinson Disease Neuroprotection Clinical Trial consortium. The objective of the this clinical trial is demonstrate the efficacy of one or several neuroprotective agents in slowing the progression of Parkinson Disease (PD) in a large, double blind, placebo-controlled clinical trial. The MSU Parkinson Disease Clinical Center will identify, enroll and maintain patients with mild, early PD (Hoehn &Yahr <2, within 5 years of symptom onset) in the pilot and Phase III trial components of this multicenter clinical trial. This proposal documents the outstanding patient recruitment and retention potential of the experienced clinical staff at MSU. Collectively, the primary investigators and the Department of Neurology at MSU have an average of nearly 700 PD patient visits and see approximately 125 new PD patients per year. Based on data from direct chart review, 55% of the new patients would meet the inclusion and exclusion criteria if patients taking symptomatic medications are included;20% would meet criteria if those taking symptomatic medications were excluded. The large pool of potentially eligible cases reflects the referral pattern for the Department of Neurology at MSU, which is the focus of primary and secondary referrals from a large area of the state that is relatively underserved by other neurologists. The central location of MSU within the state of Michigan, combined with the dispersed statewide medical school campus system, is ideal for maximal patient recruitment. Established relationships with area neurologists, local support groups and with the Michigan Parkinson Foundation, the premier statewide PD support organization, will enhance the unique recruitment base at MSU. Collaboration with the University of Michigan, as well as regional neurologists and movement disorders subspecialty providers, will foster efficient and comprehensive patient ascertainment. MSU neurologists with expertise in movement disorders will enroll and follow patients. MSU's previous experience with large, longitudinal clinical trials provide a proven track record in recruiting, retention and data acquisition in similar multi-center studies of neurological disease. MSU is an optimum environment highly successful participation in the Parkinson Disease Neuroprotection Clinical Trial.